Trunk-selecting switch for telephone systems



April 19,1921.

. 1,625,425 c. J. PRACHT V TRUNK SELECTII'QG SWITCH FOR TELEPHONE SYSTEMS 2 Sheets-Sheet 1 Original Filed June 16, 1922 To .71" JEZECMAS -Inuen mr' Earl J. ra:tTt 25mg.

C. J. PRACHT TRUNK SELECTING SWITCH FOR TELEPHONE SYSTEMS April 19, 1927. 1,625,425

-a1 Filed June 16, 1922 2 Shee ts-Sheet 2 q iL J: k- L L -Inusn [Ir- Earl 1P1" [3H Patented Apr. 19, 1927.-

units!) STATES PATENT OFFICE.

CARL J. PEACE-IT, OF CHICAGO, ILLINOIS, ASSIGNOR, BY'MESNE ASSIGNMENTS, TO

AUTOMATIC ELECTRIC INC., OF CHICAGO, ILLINOIS, A CORPORATION OF DELA- WARE.

TRUNK-SELECTING SWITCH FOR TELEPHONE SYSTEMS.

Application filed June 16, 1922, Serial No. 568,694. Renewed September 23, 1926.

The present invention relates to trunk selecting switches for telephone systems, but is more particularly concerned with the production of a secondary trunk selecting switch in which the usual switch mechanism is eliminated and relays are employed to select an idle trunk; and the principal object is the production of a new, and improved presel-ecting trunk selecting switch of the above named type, that is, one that selects trunks ahead of the calls. I

Another object is the production of a preselecting relay secondary switch that tests busy to the switches having access to it at all times except when it has an idle trunk actually ire-selected.

The above mentioned objects, together with such others as are not specifically mentioned at this time, will be pointed out more fully hereinafter, reference being had to the accompanying drawings comprising Figs. 1 and 2, in which Fig. l is a secondary trunking layout showing a typical sit-uation'in which the improved switch may be employed, while Fig. 2 shows by means of the usual circuit,

diagrams a suilicient amount of the apparatus used in connection with the improved switch to enable the invention to be thoroughly understood.

Referring now particularly to Fig. 1, this diagram shows an arrangement of primary and secondary trunks, whereby a group of first selector switches is given access on a particular level to a group oi thirty second select-or switches. The primary trunks, that is, the ones directly accessible to the first selectors, are divided into groups of ten, corresponding to the usualcapacity of a selector switch on one level, and the division into groups is carried far enough to give the required ratio between the total'number of primary trunks and the total number of secondary trunks, assumed in the present case to be the ratio of four to three. The first five trunks of each primary group, which are the ones which always become busy first,'are taken direct to second selectors and do not pass through secondary switches. This is done under the assumption that when the trafiic reaches the peak there will be at least five trunks busy out of every group of ten. The last five trunks accessible to each subgroup of first selectors or the last five It will be understood, of course, that this trunkin diagram presents nothing broadly new and that it is used merely to enable the utility of the improved secondary switch to be understood.

Referring now particularly to Fig. selector D shown therein is one of the 'subgroup which has access to the ten trunks shown in the upper left hand corner of Fig. 1. This switch is mechanically of the usual vertical and rotary type in which the bani; contacts are arranged in horizontal rows or levels. I r

The secondary switch SS, wl ich is accessible to the selector D, selects trunksby the operation of the relays 50 and 51 as will be hereinafter explain-ed. This switch has access to the selectors E and E, denoted by the dotted rectangles bearing those reference characters. The selectors E and E, it will be understood are identical with the selector D. These selectors are accessible to three other secondary switches as can be seen in Fig. 1. r

The apparatus, having been described'in general, will now'bc described in connection with a detailed description of its operation. For this purpose it will be assumed that a call is extended to theselector D by 'ay oi the trunk comprising conductors ll, 12. and i 13. When this occurs, line relay 14: energizes over the two sides of the calling line in series and closes a circuit for relca c relay 15 at armature 24. Release rclav 15, upon energizing, prepares a circuit for stepping relay 1'? and for switching relay 18 at armature 25, and at armature 26 opens a point in the circuit of release magnet 841- and prepares a circuit for vertical magnet 23.

In response to the calling of the first di it in the desired number, the circuit of line relay 14 is opened a corresponding number of times and, upon each d-eenergization of line relay 14:, the following circuit is closed for vertical magnet 23: from ground by way of the resting contact 32 and sa d armature,

2, the v armature El and its resting contact, armature. 26 and its working; contact, relay 16, and vertical magnet 23 to battery. By the ope 'ation of 'orti al i'nagnet "23, the wipers ill, 35. and 36, are 'aised step by stop until they stand oppi'isite the desired level of bank contacts. wnich level it will he assumed is the one in which the trunk a tending to the .ltiOl'lLtt 'y switch till-ii tel-urinates. Relay as is energized in series with vertical magnet 23 and, heina' slow acting, retains its arniature att acted throughout the vertical more meat. Upon the closure of all normal contacts Lt). a circuit is completed tor stepping relay l7. Stopping; relay 17. upon enerejizinn, closes a locking circuit tor itselt at armature 135%. and at armature 29 prepares circuit tor rotary magnet 21.

Bit the end oi the vertical movement, relay ll) diwnerc izes, therelw closing; a circuit lor rotary magnet 21 by way of arniature :29 and its working: contact. llotary map;- nel El, upon energizing, :ulvaraw its wipers :il. :37, an l an, into einraneinent with the first set at contacts in the level opposite where they are raised, at the same time opening; the circuit of stepping relay 17. Stepping relay l7. upon decnergziningr, opens the circuit ot rotary magnet 21 at armature 2t), and rotary magnet Ql, upon deenergrizing, closes its interrupter contacts :22 again. From this point, the operation depends upon whether the trunk terminating in the tirst fi-Ct ot taint-acts is busy or idle. It it busy the test contact thereof is grounded and stepping; relay 1''? energizes again, whereupon the wipers are advanced into engagement with the next set of banl; contacts by the energization of rotary magnet ll. This alternate operation o t stepping relay 1? and rotarj magnet 21, continues until an idle trunk is rrached, which trunk it will be assumed is the one extending to the secondary switch E .l t will he assumed further that the selector E is idle at this time and, con- ;qucntly, that relay 5i ot the secondary switch tlld h; deenerpized, as ahowu. ll ith the assumption as noted, whenthe wipers 3-l-;l(i, inclusive, arrive on the haul; contacts 31 30, inclusive, switching relay l8, which heretofore has been short circuited by the ground potential which is present upon the test contacts passed over by test wiper 3 energizes in series with stepping; relay 1T; Stepping relay 1? does not energize at t'lilS time, however, on account of the high resistance of switching relay 18. Upon energizingz switching relay l8 removes ground from the armature 0t line relay it at armature 32; opens the test circuit and pro pares the holding circuit at aru'iature 31, thereby placing g. .'ronnd From the grounded release trunk conductor 12 upon the release trunk conductor ot the secondary switch SS, so as to make the seiz d trunk busy innuediately to the other switches having access to it. This ground potential extends also by way of armature 56 and its resting contact to the release trunk conductor of the selector E, thereby rendering selector 1G busy to the other switches having; access to it. The giground potential which placed upon the rel ase, trunk conductor of the selector E extends by w y ol the restinc contactof armature 52 and said armature to the upper windiinp of relay Relay til, however, heing stitlly adjusted, does not energize i111- niediately.

Returning now to the selector l), as a still turtli r result of the energrixation of switching relay 18, it diseifinnects the ii'icoining trunk C'OlltllltttOl'S l1 and 1 troni winrjlingni oi line relay 1%; and extends them by way 0'1 ariuatures and 233 and their working cont: cts, wipers Set and 36, haul; contacts l"? and 39, the lower winding; of line relay ot the secondary switch Std, and arinalurcs 553 and 58 and their resting contacts to the upper and lower windings o t the line relay (not shown) of the selector I l. The line and re lease relays oi the selector E, which relays correspond to the line and release relays l: and 15 ot the selector l), now energize ant prepare the switch tor ope 'ation in the usual manner.

In the seconda y switch SS. line relay 5O energizes in series with the line relay ot the selector E and, upon so doings, closes a locking circuit for itself at armature 53; opens the circuit of relay 51. at armature 52 before the said relay 51 has had time to energize, and at arniatur-i 5i cuts the lower line conductor straight through and opens its own winding. Arnmture 53 adjusted to make contact with its working contact belore arinatures t2 and operate. This insau'es that armature 54 does not uhort circuit the lower winding of relay ill) het'ore the current begins to flow through the upper winding! thcrecn".

The ailing subscriber now diala the neat digit in the desired number, whereupon the selector 1) operates in the. usual manner to arise its wipers to the desired level and select an idle trunk. Illl'Qfw'PUllSl to the calling of the remaining digits in the desired number the connection is extended to the desired line in the usual manner.

ll hen the receiver is replaced at the calliinr substation, the circuit of the line relay ot the switch to which the connection has been extended is opened, whereupon the associated release relay deenergizes and opens the holding circuit oil? the selectors D and E and ot the secondary switch SS. In the secondary switch Std relay t0 deonero izes in response to ground being removed from the associated release trunk conductor, thereby restoring conditions in this switch to normal. In the selector D, switching relay 18,

ill)

upon deenergizing, closes a circuit for release magnet 40 at armature 32, which circuit extends by way of armature 24 and its resting contact, armature 26 and its resting contact, and oii" normal contacts 20. Upon the energization of release magnet 40, the wipers 34-36, inclusive, are restored to normal position in the usual manner, the circuit of release magnet 40 being opened at off normal contacts 20 by the switch shaft when the latter reaches normal position. The selector E is restored tonormal in the same manner.

Assuming now that the selector E is seized by a secondary switch other than the secondary switch. SS, a ground potential is placed on the release trunk conductor of the switch E immediately upon the switch E being seized, as hereinbefore explained, This ground potential extends by way of the resting contact oi armature 56 and said armature to the release trunk conductor of the secondary switch SS, thereby making the said secondary switch SS busy. This ground potential extends also by way of the resting contact of armature 52 and said armature to the upper winding of relay 51. Relay 51, upon energizing, prepares a locking circuit for itself at armature 57; transfers the release trunk conductor of the switc SS from the release trunk conductor of the switch E to the release trunk conductor of the switch E at armature 56, thereby removing the busy potential from the release trunk conductor'of the secondary switch SS, provided the selector E is not busy; and at armatures 55 and 53 transfers the line conductors of the secondary switch SS from the line conductors of the selector E to the corresponding conductors of the selector E. 7

As before stated, if the selector E is idle the secondary switch SS is rendered idle again. seized before the selector E becomes idle, relay 51 is then deenergized and the conductors oi the switch are again conuccted with the conductors ot' the selector E. Assuming, however, that the switch SS is seized while the switch E is busy, relay 50 energizes in series with the line relay of the selector E and'produces the circuit changes hereinbefore described. Also, relay 50, upon energizing, brings armature 59 into engagement with its working contact just before armature 52 breaks away from its resting contact, thereby closing a locking circuit for relay 51. The connection may now be completed to the desired line in the usual manner.

When the connection is released, ground is removed from the release trunk conductor of the selector E, whereupon relay 50 de energizes; opens the locking circuit of relay 51 at armature 59; and connects the upper winding of the said relay 51 with the re- It the secondary switch SS is not lease trunk conductor of the selector E at armature 52. I1": the selector E is idle at this time, relay 51 deenergizes. However, if the selector E is busy, relay 51 remains energized and the selector E remains preselected by the secondary switch SS.

The various features of the invention, having been described and ascertained in the foregoing, will be pointed out in the appended. claims.

lVhat is claimed is:

1.. In a telephone system, an outgoing trunk line, an incoming trunk line connected therewith, another outgoing trunk line, a relay, and means for energizing said relay to disconnect said incoming trunk line from the first named outgoing trunl line and to connect it with said other outgoing trunk line responsive to the first mentioned outgoing trunk line becoming busy.

2.111 a telephone system, an outgoing trunk line, an incoming trunk line connected therewith, another outgoing trunk line, a relay, means for energizing said relay to disconnect said incoming trunk line from the first named outgoing trunk line and to connect it with said other outgoing trunk line responsive to the first mentioned outgoing trunk line becoming busy, and means for preventing the energization of said relay when said first outgoing trunk line becomes busy due to seizure by way of said incoming trunk llne.

3. In a telephone system, an outgoing trunk line, an incoming trunk line connected therewith, another outgoing trunk line, a relay, means for energizing said relay to disconnect said incoming trunk line fron'i the first named outgoing trunk line and to connect it with said other outgoing trunk line responsive to the first mentioned outgoing trunk line becoming busy, and means for maintaining said relay energized inde pendent of the busy or idle condition of the first mentioned outgoing trunk line when said other outgoing trunk line is seized by way of said incoming trunk line.

l. In a telephone system, a trunk line having two branches, one normally connected and the other normally disconnected, a second trunk line similarly associated with said branches, and a relay in said first trunk line for disconnecting the first branch and for connecting the second branch whenever the first branch is in use in a connection established over said second trunk line.

5111 a telephone system, a trunk line having two branches, one normally connected and the other normally disconnected, a test conductor for said trunk line and for each branch, and a relay in said trunk line energized over the test conductor of the normally connected branch for disconnecting such test conductor from the test conductor associated with the said trunk line Ill) and toiwconnecting the last named test conductor with the test conductor associated with the normally disconnectedbranch.

(i. To a telephone system,- a trunk line having; two branches, one normally connected and the other normally disconnected, a relay energized over a conductor of the normally connected. branch for shifting the talkingcmnluctors of said trunk line from connection with the normally connected branch into coi'ineetion with the normally disconnected branch, a local circuit for maintaining said relay energized, and a second relay energized over a conductor ot said normally disconnected branch t'orclosin said local circuit.

i". The col'nbination, with an incoming line and a selection device in which said line terminates, ot a plurality of trunk lines accoeihle to said selecting device, and means in said selecting device consisting solely of relays and circuit connections theretor, tor nniintaininp; said incoming; line normally in connection with an idle one oi said trunk lines.

The combination, with an incoming trnnlr line and a selecting; device in which said trunk line terminates. of a plurality oii outgoing trunk lines accessible to said: selecting device, said incoming trunk line being normally connected to one of said outgoing trunk lines. and a relay for connecting the incon'iing' trunk line with an outgoing trunk line other than said normally connected line whenever the normally connected outgoing trunk line becon'iesbusy due to being seized independent of said device.

9. The con'ihination, with an incoming line anl a selecting); device in which said incoming line terminates, said selecting device consisting; solely oftwo relays and cire cuit connections there't'or, 0'!" two outgoing lines one of which is norn'lally connected to the incoming; line. and circuit connections for energizing only one o'l? said relays when a connection is extendedover the incoming line and the normally connected outgoing line. and for energizing both relays to extend a connection over the incomingrline and the other outgoing line.

10. In a trunking; system, a plurality of incoming lines each terniinating in a selecting derice. a group ottrunl; lines accessible to said selecting); devices in common, one 0t said trnnlc lines being normallyconnected to each incoming line at its associated selecting; device, a relay in each selecting device,

and circuit; connections efl eetire when a connection is extendedover an incoming line and the normally connected trunk llne for cne 'izrng the said relaysin the selecting devices associatedwith the other incoming lines to connect such incoming lines with one of said trunk lines other than theinoi mally connected line.

11.. In a telephone system, two outgoing trnnlcs, a plurality ot incoming trunks any one of which may seize either o'tfthe two outgoing trunks, each of the incoming trunks including a relay arranged to connect it with one of the outgoing); trunks when released and with the other when operated, means for operating each one of the said relays when the outgoing trnnlr to which it connects when released is seixed by any in coming trnnh other than the incoming: trunk with which such relay is zn-iziociated, and means for maintaining one oi said relays operated when its incomingtrout: seizes the second outgoing trunk.

In a telephone system, an incoming trunk, two outgoing trunks, a relay arrangg ml to connect said incoming trunk with one of said outgoing trunks when operated and with the other when released, airclease condnctor in each of said trunks, a second relay, an operating; circuit for said first relay controlled by a bacl; contact on the last named relay and the release conductor ol' an outgoing; trunk, another circuit for said first named relay controlled by front contacts on each of said relays, and a circuit tor said second named relay established when said incoming; trunk is seized.

13. In a telephone system, a trunk haying an incoming section and two outgoing sections, a relay associating said incoming section with one of said outgoing sections in oneposition and with the other section in another position. means establishing an: operatingand holding circuit for said relay when the first mentioned outgoing section becomes busy while the incomingsection is idle, and means for establishing; another holding circuit for said relay and openine: said operating circuit it said incoming trunlc snbsetpiently becomes busy.

l-t. In a telephone ::-:y cm. a trunkhaving an incoming sectitm and two outgoing sections, a relay association said inconiincsection with one of said outgoing sections when operated and with the other when released, means for operating; said relay under pre determined conditions, and means (merated when the incoming: trunk seized to prerentthe operation oi the relay it it has not already operated and to establish a holding circuittor-said relay itritihas already operated.

In witness whereof. I hereunto subscribe my name this 9th dayot June. A. D. 1922.

CARL J. PRAGHT. 

